Overview
ASTM C933-23: Standard Specification for Welded Wire Lath is an internationally recognized standard developed by ASTM International. This specification covers the requirements for welded wire lath, both flat and self-furring varieties, used as a supportive base for Portland cement-based interior plaster and exterior stucco applications. The standard outlines the composition, dimensions, physical properties, packaging, marking, and quality assurance characteristics necessary to ensure the structural performance and reliability of welded wire lath in both residential and commercial construction projects.
Welded wire lath, according to ASTM C933-23, is fabricated from cold-drawn, galvanized steel wire. It can be supplied with or without factory-attached backing materials such as water-resistive barriers. These barriers, when present, enhance the performance of the lath in demanding stucco and plaster installations.
Key Topics
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Material Requirements:
Welded wire lath must be manufactured from cold-drawn, zinc-coated (galvanized) steel wire that complies with specific ASTM and federal standards for thickness, coating, and durability.
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Construction & Dimensions:
- Openings within the lath are restricted to a maximum of 2 x 2 inches (51 mm x 51 mm).
- Reinforcement may be added parallel to the lath’s long dimension, improving strength and durability.
- The lath may include self-furring crimps that project from the back, providing space for plaster embedment.
- Standard dimensions are strictly defined to ensure compatibility with various wall assemblies.
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Water-Resistive Barrier Backing:
When provided, the factory-attached backing must adhere securely to the lath and meet specified requirements for water resistance and bursting strength. This backing is critical in exterior stucco systems to manage moisture and prevent detachment during shipping or installation.
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Packaging & Marking:
Bundles or rolls of welded wire lath are to be visibly and permanently marked with details such as manufacturer, country of origin, product description, mesh size, and wire thickness, ensuring traceability and compliance verification.
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Inspection, Sampling, and Rejection:
The standard includes guidelines for sampling and inspecting products, as well as procedures for identifying and reporting nonconforming materials.
Applications
Welded wire lath specified by ASTM C933-23 plays a vital role in modern construction by providing a stable base for Portland cement-based plasters and stucco. Key applications include:
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Exterior Stucco Systems:
Providing necessary reinforcement and anchorage for cement-based stucco on building exteriors, enhancing durability and resistance to cracking.
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Interior Plaster Walls and Ceilings:
Serving as a supportive grid that helps plaster or render bond securely to substrates in both residential and commercial interiors.
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Masonry Veneer Base:
Used as an intermediate layer to support thin masonry or stone veneer installations over wood or steel framing.
This standard ensures that welded wire lath components perform reliably, readily integrating with industry best practices for moisture management and structural stability.
Related Standards
- ASTM A641/A641M: Standard Specification for Zinc-Coated (Galvanized) Carbon Steel Wire, referenced for material quality and galvanization requirements.
- ASTM C11: Terminology Relating to Gypsum and Related Building Materials and Systems, used for consistent language and definitions.
- ASTM E2556/E2556M: Specification for Vapor Permeable Flexible Sheet Water-Resistive Barriers, applicable to optional factory-attached backings.
- Federal Specification UU-B-790: Building Paper for water-resistant backing material.
For additional details, consult the latest version of ASTM C933-23 and the above referenced standards to ensure compliance, safety, and performance in all applications involving welded wire lath systems.